1. Field of the Invention
This invention relates generally to fiber optic light detectors and, more particularly, to fiber optic light detectors on which a fiber optic bundle can be accurately placed to completely cover the photocell in the detector.
2. Description of the Prior Art
The use of fiber optic bundles is relatively widespread, especially in the fields of medicine and dentistry. The fiber optic bundle in conjunction with a light source is generally known as a cold light source. In the medical/dental field, the fiber optic bundle is used to direct light at an area under investigation. The fiber optic can be in the form of a plurality of individual strands formed together into a sheath, or a single rod encased in a sheath. Both of these will hereinafter be referred to as fiber optic bundles.
Basically, a fiber optic light source comprises a fiber optic bundle which is illuminated by a high intensity, high wattage lamp. The fiber optic bundle may be several feet long and is positioned in a housing with respect to the lamp so that the filament of the lamp transfers maximum light to the fiber optic bundle. The fiber optic bundle is used to direct light from the light source to any desired position. A dentist might use the fiber optic light source to aid in curing material used to repair teeth. For such use, light of a specific intensity is needed.
Various manufacturers make fiber optic bundles of different diameters. The typical diameter of such bundles can vary between 3/32" to 1/2" or more.
Fiber optic light detectors are generally well known and are used for sensing the light intensity of fiber optic bundles illuminated by a light source. The fiber optic light detector contains a photocell. A fiber optic bundle, whose intensity is desired to be measured, is placed to cover the photocell. When the photocell is covered it measures the light intensity of the fiber optic bundle. To obtain an accurate reading, the photocell should be completely covered.
Prior attempts at completely covering the photocell are illustrated in FIGS. 1 and 2. FIG. 1 illustrates a device in which a target was placed around the photocell 52. This represents a bull's eye target 62, with the photocell 52 being the bull's eye. The fiber optic bundle illuminated by the lamp of a light source is then placed over the bull's eye target 62 in a manner to cover the photocell 52. The circles surrounding the photocell 52 are provided as guides for correctly positioning the fiber optic bundle. The different sized circles in the target account for alignment with different sized fiber optic bundles. This device does not include components which will aid in holding fiber optic bundles in a position in which they will cover the photocell for the period necessary to obtain an accurate reading of the light intensity. The fiber optic bundles are therefore apt to move and if not covering the photocell will produce an inaccurate reading.
FIG. 2 illustrates another approach using a step device. The photocell 52 is positioned at the bottom of a well 64 with steps 66 surrounding the photocell 52 leading out of the well 64. A fiber optic bundle is then placed over the well 64 at the deepest level to which it can fit based on the size of the fiber optic bundle. The light source is then activated and an intensity reading is taken by the photocell 52. If the fiber optic bundle does not fit snugly into a step, it is apt to slide around within the step and distort the reading. Another problem with such a device is that the steps provide a distance between the fiber optic bundle and the photocell. This distance can result in an erroneous measurement.
An example of an apparatus for accommodating various diameter fiber optic bundles is described in U.S. Pat. No. 4,397,523 issued Aug. 9, 1983. This patent describes an arrangement whereby the fiber optic bundle will be centrally positioned with respect to a light. It uses three movable pins, each at 120.degree. around a central axis which can move radially in and out as a surrounding knob is rotated. These pins maintain the central position of the fiber optic bundle regardless of its diameter by adjusting the inward and outward movement of these pins. This device is used for clamping a fiber optic bundle to a light source. Another example of a device for positioning a fiber optic with respect to a light source is shown in U.S. Pat. No. 4,768,199 issued Aug. 30, 1988. This patent uses a "V" groove for positioning the fiber optic so that it will be co-axial with a laser light.
Although these devices attempt to sense the light intensity of fiber optic bundles and are adapted for positioning of fiber optic bundles to cover a photocell or light source, they are not necessarily very accurate. They do not provide a device which will insure complete coverage of the photocell while sensing the intensity of the light source. These devices thus allow for the possible introduction of ambient light when the photocell is not completely covered. Certain of these devices also allow for a distance between the photocell and the fiber optic bundle. Due to this distance, the intensity of the light is diminished at the point of the photocell.
It is, therefore, needed to produce a fiber optic light detector which solves the aforementioned problems and provides improvements over the presently known devices for measuring the intensity of a light source.